How Panorama Programs Stitch
Several Photos into One Superwide
178 PART 3 HOW THE DIGITAL DARKROOM WORKS
We like our pictures to be wide. We like the wide screens of IMAX and HDTV. If a landscape
photo is awe-inspiring, it inspires even more awe the wider it is. There’s no explanation why
we are so impressed by elongated dimensions, but photographers have been shooting
panoramas since the first panorama camera was built in 1843. From then until the advent of
the digital camera, panoramas were shot with specially built cameras. Digital photography
lets us combine two or more photos taken with ordinary cameras into one wide, mind-
blowing panorama. Here’s how it’s done, all without human intervention, by Autostitch, a
program created by Matthew
Brown and David Lowe at the
University of British Columbia
(free at http://www.cs.ubc.ca/
~mbrown/autostitch/
autostitch.zip).Stitchingsoftware, part of many photo editing programs,
joins several photos into one panorama. Most require human
intelligence to judge when individual photos are fitted together
properly. Autostitch uses artificial intelligence to make the deci-
sions, including what images selected from a directory full of
photos are ripe for stitching, and pieces them with no human
directions.1
Autostitch begins by examining
all the photos in a directory for
features that areinvariant—
that is, features that resist basic
changes even if they are
enlarged, rotated, or seen from
a slightly different perspective.
This is done in a search called
aSIFT(scale-invariant feature
transform).2